Diana famously visited the hospital in 1989, shaking hands with an AIDS patient before kissing him on the cheek. The Princess' contact with the patient without wearing gloves went a long way in reducing stigma against the illness at the time.

"HIV does not make people dangerous to know," Diana was famously quoted. "You can shake their hands and give them a hug. Heaven knows they need it."

Harry's quiet visit to Mildmay marks a follow-up to the one he made last December, and the latest in his effort to fight AIDS.

"When my mother held the hand of a man dying of AIDS in an East London hospital, no one would have imagined that just over a quarter of a century later, treatment would exist that could see HIV-positive people live full, healthy, long lives," he said. "It is time for us to step up and acknowledge that stigma and discrimination still act as the greatest barrier to us defeating this disease once and for all."